In large scale food processing systems, a desired attribute of an oven is to provide desired cooking characteristics of particular food products as quickly as possible to obtain high throughput from the oven. In such ovens, a continuously running conveyor is conventionally used to introduce food products to the oven on a continuous basis, with the conveyor running from an entrance or inlet opening to an exit or outlet opening associated with the oven. Such systems have included use of both linear and spiral or helical conveyors. These ovens accommodate a large amount of food products therein, and provide the predetermined dwell time to allow thorough and complete cooking of any particular type of food product desired.
The cooking atmosphere of such ovens has been conventionally provided by means of burner units which introduced a heated gas cooking medium by means of a flame source, or alternatively by the introduction of steam into the oven chamber. For many applications, the moisture level in an oven is maintained by the injection of steam into the cooking atmosphere. In an oven atmosphere containing high steam content, significant heat losses are normally found at the entrance and exit locations of a continuous conveyor belt associated with the oven. Although attempts have been made to produce steam ovens having a cooking atmosphere with high humidity, such attempts have not resulted in an oven which optimizes efficient use of steam injected into the oven to transfer heat to food products introduced into the oven. In known oven configurations, attempts have been made to create a steam atmosphere near 212.degree. F. and 100% humidity at one atmosphere, with such an atmosphere created by introducing large amounts of steam into the oven to produce an oven atmosphere at a pressure which is above atmospheric. Such ovens have included exhaust ducts at the location of the inlet and outlet areas of a conveyor belt associated with the oven, which exhausts escaping gases from the oven. Although attempts have been made to reduce losses of steam and heat energy from such an oven, such attempts have not resulted in systems which substantially reduce flow rates of steam from the oven to increase efficiency of performance and maintain introduced steam in the cooking atmosphere.